Sizing of a workpiece bore in small increments with a plurality of abrading tools of different fixed diameter is shown in U.S. Pat. No. 4,291,504 issued Sept. 29, 1981 of common assignee herewith. In this sizing process, each tool diameter is initially adjusted to a preselected fixed diameter increasing from one tool to the next and the workpiece bore is exposed successively to the increasing diameter tools. Each tool is passed through the bore from one end to the other and then withdrawn by reverse movement to constitute a single pass working cycle. Stock removal capability per cycle is comparatively low and is usually limited to a few thousandths of an inch. Although a single tool single pass system may be employed, it is common when stock removal requirements exceed the capability of a single tool single pass operation to provide multiple spindles and tools successively removing less stock with finer grit size and larger diameter abrading tools, thereby qualifying the bore for the next single pass tool. This technique is advantageous for sizing bores to extremely narrow limits of size, roundness and straightness.
The tool employed typically includes an adjustable abrading sleeve or multiple stones engaged by a tapered arbor. In the past, the tool has been preset to the fixed single pass diameter by manually turning threaded nuts which slide the abrading sleeve or stones and arbor relative to one another; i.e. as shown in the Fitzpatrick U.S. Pat. No. 4,173,852 issued Nov. 13, 1979 and copending application U.S. Ser. No. 305,008 entitled "Fixed Diameter Single Pass Abrasive Tool with Multi-Layer Inserts" filed in the name of the present inventor and of common assigne herewith. This same manual adjustment arrangement has also been employed in adjustment of the abrading tool to compensate for wear after long machining runs often comprising several thousand parts. Wear of individual tools is sensed by so-called gage plugs such as those described in the previously referenced U.S. Pat. No. 4,291,504. Another abrading tool employing manual tool diameter adjustment by threaded nuts is described in U.S. Pat. No. 4,199,903 issued Apr. 28, 1980.
Prior art patents disclose expandable cutting tools for applications other than incremental sizing of bores, in particular for honing, reaming and lapping. For example, the Roebbel and Rogers U.S. Pat. No. 1,828,074 describes a honing or lapping tool in which an adjusting rod extending through a hollow tapered arbor pulls an external sleeve against the stones and slides them along the tapered arbor for diameter expansion. The adjusting rod is actuated manually by a threaded nut and collar. The abrading members of the tool of the Beard U.S. Pat. No. 1,874,856 are expanded or contracted in diameter by a manually-operable threaded nut/collar arrangement at opposite ends of the abrading members. A somewhat similar arrangement is illustrated in the Sims U.S. Pat. No. 1,960,555. A simple collar arrangement is provided in the Speck U.S. Pat. No. 2,694,277 for adjusting the diameter of the abrading sleeve. Adjustment is effected by striking one of the positioning collars located at opposite ends of the abrading sleeve.
A multiple spindle honing machine is shown in Greenburg U.S. Pat. Nos. 2,757,488 and 3,286,409. In these patents, the honing stones are carried at lower ends of hollow shanks. The upper ends of the shanks are attached to rotatable hollow spindles which in turn are journaled on a reciprocable machine head. Hone expander rods include conical cams at their lower ends to engage the honing stones for expansion purposes and extend through the shanks and spindles into the machine head. Each expander rod terminates in a threaded end coupled to threaded nut journaled in the machine head and having a flange in the form of a worm wheel. A power actuator mechanism including a pair of electric motors and worm gear is provided for driving the worm wheel to translate the expander for hone diameter adjustment. U.S. Pat. Nos. 2,787,865 and 2,787,866 issued to Gross also disclose power actuator means for actuating a hone expander rod. And, the Seborg U.S. Pat. No. 2,870,577 describes a long expander rod which carries a lateral pin with the pin riding in a helical inner groove on a sleeve member. A rack bar meshes with a gear on the sleeve member to rotate the latter, causing the hone expander rod pin to ride up or down in the helical groove and raising or lowering the expander rod.
The Fitzpatrick U.S. Pat. No. 4,187,644 discloses another multiple spindle honing machine in which hydraulic feed cylinders are mounted on a reciprocable spindle head with a connector rod operatively connecting one of the feed cylinders with a respective honing tool. Each connector rod comprises first and second threaded members secured together by a threaded coupling. The rods extend from the feed cylinders through a hollow drive member and have a lower end with conical cams for radially expanding the honing stones. The feed cylinders provide initial expansion of the honing tools upon spindle head movement while a constant feed mechanism assumes expansion of all the tools at a constant rate during the honing operation. The constant feed mechanism includes a gear rack which meshes with the second threaded member of the connector. Machine operation is automatically terminated by a switch mechanism when excessive honing stone wear is sensed. Similarly, the honing tools are auomatically collapsed by switch means when a gauge plug detects that the proper bore size has been reached. U.S. Pat. Nos. 2,741,071 and 2,845,752 issued to Calvert and U.S. Pat. No. 2,797,531 issued to Seborg also disclose hydraulically actuated hone expander rods.